Process for making electrically conductive images



United States Patent Oifice 3,464,822 Patented Sept. 2, 1969 3,464,822PROCESS FOR MAKING ELECTRICALLY CONDUCTIVE IMAGES Ralph Kingsley Blake,Westfield, N.J., assignor to E. I. du Pont de Nemours and Company,Wilmington, Del. a corporation of Delaware No Drawing. Filed Sept. 13,1965, Ser. No. 487,031 Int. Cl. G03c 5 /54; C23b 5 48 US. Cl. 9638.4 9Claims ABSTRACT OF THE DISCLOSURE A process which comprises (a) Forminga latent developable silver halide image in a photographic elementhaving a water-permeable, macromolecular organic colloid-silver halideemulsion layer, by imagewise exposure of said layer to actinicradiation,

(b) Forming by silver transfer development by means of a developersolution containing a silver halide developing agent, a silver halidesolvent and a silver nucleating agent, an electrically conductive silversurface image having a resistance not more than 5.0 ohms per square inthe unexposed areas of an outer water-permeable organic colloid layer ofsaid photograhic film element, and a difference in resistivity of atleast 1X10 times between the conductive coating and the exposed regions,and

(c) Passing an electrical current or impulse through the saidelectrically conductive silver surface image for utilization.

This invention relates to a process for making electrically conductivesilver images, or, more specifically, to a photographic method for thepreparation of electrically conductive silver surface images. Even morespecifically, this invention relates to a new process for thepreparation by silver transfer development of elements containingelectrically conductive silver surface images from photographiclight-sensitive elements. This invention also relates to the productproduced by this novel process where said product contains electricallyconductive silver surface images.

Normal chemical development of the typical silver halide photographiclight-sensitive emulsion gives developed silver images that have almostno electrical conductance. For certain purposes it is desirable to makesilver surface images which conduct electricity. Such images can be usedas a printed circuit. The prior art has disclosed a method of forming anelectrically conductive silver surface image on the surface of a silverhalide photographic emulsion. The electrically conductive silver surfaceimages produced by the novel process of this invention are superior tothe prior art silver surface images, in that, among other reasons, thesilver surface image has far lower electrical resistivity.

It is an object of this invention to produce a new improved producthaving electrically conductive silver surface images. Another object ofthis invention is to obtain a product having electrically conductivesilver surface images which have essentially nonconductive backgrounds.A further object is to make conductive images rapidly and, wheredesired, on a flexible support. A further object of this invention is toobtain an electrically conductive silver image on the surface of thephotographic element which can be used as a printed circuit board. Stillfurther objects will be apparent from the following description of theinvention.

The process for photographically forming the positive electricallyconductive elements of this invention in its broader aspects comprises(a) Forming a latent developa-ble silver halide image in a photographicelement having a water-permeable, macromolecular organic colloid-silverhalide emulsion layer, by imagewise exposure of said layer to actinicradiation.

(b) Forming by silver transfer development an electrically conductivesilver surface image having a resistance not more than 5.0 ohms persquare in the unexposed areas of an outer water-permeable colloid layerof said photographic film element and a difference in resistivity of atleast l 1() times between the conductive coating and the exposedregions, and

(c) Passing an electrical current or impulse through the saidelectrically conductive silver surface image for utilization of thecurrent or impulse.

The silver halide surface image can be formed in the original silverhalide emulsion layer or in a contiguous water-permeable, oleophobic,macromolecular organic colloid layer initially free from thelight-sensitive silver salts.

In the process, the imagewise exposure preferably is carried out to forma printed circuit image for a machine, apparatus, instrument, dial or acomponent thereof, and the current or impulse utilized in the reverseprinted circuit image having a resistivity of from about 0.1 to 5.0 ohmsper square to control or actuate a part or parts of such an article.

This invention is not restricted to the use of the specific processingsolutions and exposure conditions disclosed in the following specificdescription and in the detailed or working examples.

A surface has adequate electrical conductivity for use in accordancewith this invention when the resistance is not greater than 5 .0 ohmsper square. Electrically conductive silver surface images having anelectrical resistivity of about 0.1 ohm per square are obtained readilyin accordance with this invention.

Conventional, low silver halide solvent, photographic developers reduceexposed areas of a silver halide element to a negative silver image.When a silver halide solvent and a nucleating agent are added to lowsolvent developers, a conventional negative image also forms, but silvertransfer, by the diffusion of silver complex ions to the surface of thelayer, takes place in the unexposed areas where they reduce to form anelectrically conductive positive silver image. Since an inverse orreverse image forms, this type of development is often known as inversetransfer development. If the developer is too slow in its action, anelectrically conductive surface silver image having a resistivity notgreater than 5.0 ohms per square will not form. Electrically conductiveimages are Obtained on the surface of exposed film by inverse transferdevelopment using certain monoand dual-bath developing solutions. Ingeneral, when a sulfide compound and a thiocyanate compound, or theirrespective equivalents are added to a high energy developer,electrically conductive silver surface images having a resistance notmore than 5.0 ohms per square can be formed. A high energy developer isdefined as any developer that develops seventy-five percent of the totaldevelopable density in one minute.

A dual-bath developer as described herein is used in the preferredembodiment of the invention. A major reason for preferring thisdeveloper is that is assures high electrical resistivity in thebackground regions, that is, the exposed regions. By developing thebackground first, no exposed silver halide remains to dissolve in thesecond developer containing a high concentration of silver halidesolvent, and the difference in resistivity of the exposed and unexposedregions is kept to a maximum.

Electrically conductive silver surface images fonm when a single-agentconventional low solvent developer, containing additional silver halidesolvent and a nucleating agent,

is used. Single-agent developer means a developer bath containing asingle developing agent; a two-agent developer means a developer bathcontaining two developing agents, etc. A mono-bath developer means adeveloper consisting of a single developing bath; a dual-bath developermeans a developer consisting of two developing baths, etc.

The preference for a two-agent developer of the type specified isemphasized in the case of a film which is classified in the art as aslow developing film. In developing this type film, a two-agentdeveloper is aided by increasing solution pH to increase developingrate.

In the unexposed areas during development, it is believed that thesilver halide migrates to or near the surface of the film as a complexion. The nucleating agents, having permeated the surface region,catalyze the reduction of the silver halide complex to metallic silverin the presence of the developing agent.

The following examples illustrate this invention but are not intended tolimit it in any way.

EXAMPLE I The first developer solution, Solution A, of a dualbathdeveloper was prepared as follows:

Water ml 800 l-phenyl-3-pyrazolidone (reagent grade) gm 0.25 Ascorbicacid (reagent grade) gm 2.5 Potassium carbonate (anhydrous) gm 5 Sodiumhydroxide grams dissolved in sufiicient water to make up 100 ml. ofsolution) ml 5 Water to make up to 1000 ml.

The method developer solution, Solution B, was prepared as follows:

Water ml 600 Sodium sulfite (anhydrous) gm 120 Hydroquinone (anhydrous)gm 4 1-phenyl-3-pyrazolidone (reagent grade) gm 0.25 Boric acid (H BO(crystals) gm 5.5 Sodium hydroxide (10 grams dissolved in sufiicientwater to make up to 100 ml. of solution) ml 180 Sodium sulfide (1 gramdissolved in sufficient water to make up 100 ml. of solution) ml 8S-nitrobenzimidazole nitrate (reagent grade) (1 gram dissolved insufficient ethanol and water, in equal portions, to make up 100 ml. ofsolution) ml Potassium thiocyanate (anhydrous) gm Water to make up to1000 ml.

A photographic film of the lithographic type was exposed at a distanceof 26 inches for seconds to a high intensity tungsten filament lamp (aNo. 2 General Electric Photofiood lamp) operated at 13 volts, A.C.Exposure was to a line pattern having a uniform silver density of 1.4which is intended to simulate a camera exposure. The film comprised ahigh contrast silver chlo ride-silver bromide emulsion, in which thesilver salt contained mol percent silver bromide and 70 mol percentsilver chloride, and which contained grams of gelatin per mole of silverhalide, and a polyester base. The exposed film was immersed in SolutionA for two minutes and then washed with water for two minutes. Theexposed film was immersed in Solution B for two minutes and then washedwith water for two minutes. The film was dried at room temperature. Adeveloped image (that is, a negative image) was obtained with thenormally undeveloped areas having a continuous, silver metal, positivecoating which latter coating is electrically conductive. The measurementohms per square is defined as one one-hundredth of the resistivity, inohms, of a line 100 times longer than its width. The probes of a WestonModel 785 Industrial Circuit Tester were placed at each end of a linethat was 100 squares long. The resistivity of the line was measured as10 ohms.

This represents a surface resistivity of 0.1 ohm per square, therebyshowing that this coating was capable of conducting an electricalcurrent. A measurement of the background, i.e., exposed regions, showedthat those regions had an electrical resistivity of greater than 3 10ohms per square (the upper measurement limit of the meter used). Adifference in resistivity of approximately 1 10 times between theconductive coating and the background regions will assure that there isno leakage of the electrical current into the background regions, orcurrent passage between two separate and distinct conductive coatings.This essential difference is greatly exceeded by the final film elementin this example.

EXAMPLE II The first developer solution, Solution A, of a dual-bathdeveloper was prepared using the method described in Example I forpreparing Solution A.

The second developer solution, Solution C, of a dual- Water to make upto 1000 ml.

A photographic film of the lithographic type as described in Example Iwas exposed as described in Example I. The exposed film was immersed inSolution A for two minutes and then Washed with water for two minutes.The exposed film was immersed in Solution C for two minutes and thenWashed with Water for two minutes. The film was dried at roomtemperature. A developed image was obtained with the normallyundeveloped areas having a continuous, silver metal, positive coatingwhich latter coating is electrically conductive. The surface areas ofthe film were measured for electrical conductivity. The unexposedregions of the film were electrically conductive, while in the exposedregions the gray silver image was nonconductive. The electricallyconductive surface image had a resistivity of 0.1 ohm per square.

EXAMPLE III The first developer solution, Solution A, of a dualbathdeveloper was prepared using the method described in Example I forpreparing Solution A.

The second developer solution, Solution D, of a dualbath developer wasprepared as follows:

Water to make up to 1000 ml.

A photographic film of the lithographic type as described in Example Iwas exposed as described in Example I. The exposed film was immersed inSolution A for two minutes and then washed with water for two minutes.The exposed film was immersed in Solution D for two minutes and thenwashed with water for two minutes. The film was dried at roomtemperature. A developed image was obtained with the normallyundeveloped areas having a continuous, silver metal, positive coatingwhich latter coating is electrically conductive. The surface areas ofthe film were measured for electrical conductivity. The unexposedregions of the film were electrically conductive while in the exposedregions the gray silver image was nonconductive. The electricallyconductive surface image had a resistivity of 0.5 ohm per square.

EXAMPLE IV The first developer solution, Solution A, of a dual-bathdeveloper was prepared using the method described in Example I forpreparing Solution A.

The second developer solution, Solution E, of a dualbath developer wasprepared as follows:

Water ml 500 Sodium sulfite (anhydrous) gm 120 Hydroquinone (anhydrous)gm 48 l-phenyl-3-pyrazolidone gm 3 Boric acid (H BO (crystals) gm 5.5Potassium thiocyanate (anhydrous) gm 160 S-nitrobenzimidazole nitrate(reagent grade) (1 gram dissolved in sufficient ethanol and water, inequal portions, to make up 100 ml. of solution) ml 30 Sodium sulfide (1gram dissolved in sufficient water to make up 100 ml. of solution) ml 8Sodium hydroxide (10 grams dissolved in sufiicient water to make up 100ml. of solution) ml 180 Water to make up to 1000 ml.

A photographic film of the lithographic type as described in Example Iwas exposed as described in Example I. The exposed film was immersed inSolution A for two minutes and then washed with water for two minutes.The exposed film was immersed in Solution E for two minutes and thenwashed with water for two minutes. The film was dried at roomtemperature. A developed image was obtained with the normallyundeveloped areas having a continuous, silver metal, positive coatingwhich latter coating is electrically conductive. The surface areas ofthe film were measured for electrical conductivity. The unexposedregions of the film were electrically conductive, while in the exposedregions the gray silver image was nonconductive. The silveryelectrically conductive surface image had a resistivity of 1 ohm persquare.

EXAMPLE V The first developer solution, Solution A, of a dual-bathdeveloper was prepared using the method described in Example I forpreparing Solution A.

The second developer solution, Solution F, of a dualbath developer wasprepared as follows:

Sodium sulfide (1 gram dissolved in sutficient water to make up 100 ml.of solution) ml 8 Water to make up to 1000 ml.

A photographic film of the lithographic type as described in Example Iwas exposed as described in Example I. The exposed film was immersed inSolution A for two minutes and then washed with water for two minutes.The exposed film was immersed in Solution F for two minutes, and thenwashed with water for two minutes. Then film was dried at roomtemperature. A developed image was obtained with the normallyundeveloped areas having a continuous, silver metal, positive coatingwhich latter coating is electrically conductive. The surface areas ofthe film were measured for electrical conductivity. The unexposedregions of the film were an electrically conductive image, While in theexposed regions the gray silver was nonconductive. The electricallyconductive surface image had a resistivity of 2.5 ohms per square.

EXAMlPLE VI The first developer solution, Solution A, of a dual-bathdeveloper was prepared using the method described in Example I forpreparing Solution A.

The second developer solution, Solution G, of a dualbath developer wasprepared as follows:

Water ml 600 Sodium sulfite (anhydrous) gm Hydroquinone (anhydrous) gm 81-phenyl-3-pyrazolidone gm 0.5 Boric acid (H BO (crystals) gm 5.5Potassium thiocyanate (anhydrous) gm 32 S-nitrobenzimidazole nitrate(reagent grade) (1 gram dissolved in sufiicient ethanol and water, inequal portions, to make up 100 ml. of solution) ml 30 Sodium hydroxide(10 grams dissolved in suflicient water to make up 100 ml. of solution)ml Sodium sulfide (1 gram dissolved in sufiicient water to make up 100ml. of solution) ml 0.4

Water to make up to 1000 ml.

A photographic film of the lithographic type as described in Example Iwas exposed as described in Example I. The exposed film was immersed inSolution A for two minutes and then washed with water for two minutes.The exposed film as immersed in Solution G for two minutes and thenwashed with water for two minutes. The film was dried at roomtemperature. A developed image was obtained with the normallyundeveloped areas having a continuous, silver metal, positive coatingwhich latter coating is electrically conductive. The surface areas ofthe film were measured for electrical conductivity. The unexposedregions of the film were electrically conductive, while in the exposedregions the gray silver image was nonconductive. The electricallyconductive surface image had a resistivity of 0.25 ohm per square.

EXAMPLE VII The first developer solution, Solution A, of a dual-bathdeveloper was prepared using the method described in Example I forpreparing Solution A.

The second developer solution, Solution H, of a dualbath developer wasprepared using the method described in Example VI for preparing SolutionG, except that 40 ml. of sodium sulfide solution were used in preparingSolution H.

A photographic film of the lithographic type as described in Example Iwas exposed as described in Example I. The exposed film was immersed inSolution A for two minutes and then washed with water for two minutes.The exposed film was immersed in Solution H for two minutes and thenwashed with water for two minutes. The film was dried at roomtemperature. A developed image was obtained with the normallyundeveloped areas having a continuous, silver metal, positive coatingwhich latter coating is electrically conductive. The surface areas ofthe film were measured for electrical conductivity. The unexposedregions of the film were electrically conductive while in the exposedregions the gray silver image was nonconductive. The electricallyconductive surface image had a resistivity of 1.5 ohms per square.

EXAMPLE VIII The first developer solution, Solution A, of a dual-bathdeveloper was prepared using the method described in Example I forpreparing Solution A.

The second developer solution, Solution I, of a dualbath developer wasprepared as follows:

-nitrobenzimidazole nitrate (reagent grade) (1 gram dissolved insufficient ethanol and water, in equal portions, to make up 100 ml. ofsolution) ml 30 Sodium hydroxide grams dissolved in suflicient water tomake up 100 ml. of solution) ml 180 Sodium sulfide (1 gram dissolved insutficient water to make up 100 ml. of solution) ml 78 Water to make upto 1000 ml.

A photographic film of the lithographic type as described in Example Iwas exposed as described in Example I. The exposed film was immersed inSolution A for two minutes and then washed with water for two minutes.The exposed film was immersed in Solution I for two minutes and thenwashed with water for two minutes. The film was dried at roomtemperature. A developed image was obtained with the normallyundeveloped areas having a continuous, silver metal, positive coatingwhich latter coating is electrically conductive. The surface areas ofthe film were measured for electrical conductivity. The unexposedregions of the film were electrically conductive while in the exposedregions the gray silver image was nonconductive. The electricallyconductive surface image had a resistivity of 4.0 ohms per square.

EXAMPLE IX The first developer solution, Solution A, of a dual-bathdeveloper was prepared using the method described in Example I forpreparing Solution A.

The second developer solution, Solution J, of a dualbath developer wasprepared using the method described in Example VI for preparing SolutionG, except that none of the sodium sulfide solution was used in preparingSolution J.

A photographic film of the lithographic type as described in Example Iwas exposed as described in Example I. The exposed film was immersed inSolution A for two minutes and then washed with water for two minutes.The exposed film was immersed in Solution J for two minutes and thenwashed with water for two minutes. The film was dried at roomtemperature. A developed image was obtained with the normallyundeveloped areas having a continuous, silver metal, positive coatingwhich latter coating is electrically conductive. The surface areas ofthe film were measured for electrical conductivity. The unexposedregions of the film were electrically conductive while in the exposedregions the gray silver image was nonconductive. The electricallyconductive image had a resistivity of 0.8 ohm per square.

The other pieces of photographic film of the type described in Example Iwere exposed and developed as described above, except that the firstpiece of film was developed for 1 minute in Solution 1 and the secondpiece of film was developed for 4 minutes in Solution J. Theelectrically conductive surface image of the first piece and secondpiece had a resistivity of 3.5 and 0.25 ohm per square, respectively. Ingeneral, those high-energy developers containing a sulfide and a silverhalide solvent have an optimum processing time of about two minutes.

Sample N o.

With a processing time of much over two minutes, the electricallyconductive image starts to turn to silver sulfide, and, with aprocessing time much under two minutes, there is not suflicient time forthe silver image to properly form. In either case, the result is lowerconductivity than could be obtained. However, for a developer which doesnot have any sulfide as a starting constituent, that is, one using thesilver halide solvent, a thiocyanate compound, as the nucleating agent,no such optimum processing time is found. In that case, the imageconductivity increases with development time until it reaches someplateau, and any processing beyond this plateau time does not appear todecrease the conductivity.

EXAMPLE X A mono-bath developer, Solution I, was prepared using themethod described in Example VI for preparing Solution G, except that nosodium sulfide solution was used in preparing Solution J.

Twelve pieces of photographic film of the lithographic type described inExample I were exposed as described in Example I. These pieces ofexposed film were processed as follows:

Time of developm ent in Solution .1 (min) Time of predevelopment wash(min.)

Was a conductive image formed? ewermwrozocncnenoo wreww-zewmzeww-mw 1Seconds.

These data show that a pro-development water wash for the exposed filmwill allow the formation of an electrically conductive image in theunexposed regions when a mono-bath developer containing high energydevelopers, among other constituents, is used.

EXAMPLE XI The first developer solution, Solution A, of a dual-bathdeveloper was prepared using the method described in Example I forpreparing Solution A.

The second developer solution, Solution K, of a dualbath developer wasprepared as follows:

Water ml 600 Sodium sulfite (anhydrous) gm 133 Hydroquinone (anhydrous)gm 2.7 1-phenyl-3-pyrazolidone gm 0.17 Boric acid (H BO (crystals) gm 4Sodium hydroxide (10 grams dissolved in suflicient water to make up ml.of solution) ml 45 Sodium sulfide (1 gram dissolved in sufiicient waterto make up 100 ml. of solution) ml 5 Water to make up to 1000 ml. pH 211.5.

A photographic film was exposed as described in Example I. The filmcomprised a silver chloride emulsion, which contains 46.8 grams ofgelatine per mole of silver chloride, that is overcoated with a clear,hardened gelatin layer, and a polyester base. The exposed film wasimmersed in Solution A for two minutes and then washed with water fortwo minutes. The exposed film was immersed in Solution K for six minutesand then washed with water for two minutes. The film was dried at roomtemperature. A developed image was obtained with the normallyundeveloped areas having a continuous, silver metal, posi tive coatingwhich latter coating is electrically conductive. The surface areas ofthe film were measured for 9 electrical conductivity. The unexposedregions of the film were electrically conductive while in the exposedregions the gray silver image was nonconductive. The silveryelectrically conductive surface image had a resistivity of ohms persquare.

EXAMPLE XII The first developer solution, Solution A, of a dualbathdeveloper was prepared using the method described in Example I forpreparing Solution A.

The second developer solution, Solution L, of a dualbath developer wasprepared as follows:

Water ml" 700 Sodium sulfite (anhydrous) grn 105 Hydroquinone(anhydrous) gm 4.0 1-phenyl-3-pyrazolidone gm 0.25 Potassium carbonategm 22 Potassium thiocyanate (anhydrous) gm 30 Sodium sulfide 1 gramdissolved in sulficient water to make up 100 ml. of solution) ml 8 Waterto make up to 1000 ml.

A photographic film of the lithographic type as described in Example Iwas exposed as described in Example I. The exposed film was immersed inSolution A for two minutes and then washed with water for two minutes.The exposed film was immersed in Solution L for two minutes and thenwashed with water for two minutes. The film was dried at roomtemperature. A developed image was obtained with the normallyundeveloped areas having a continuous, silver metal, positive coatingwhich latter coating is electrically conductive. The surface areas ofthe film were measured for electrical conductivity. The unexposedregions of the film were electrically conductive while in the exposedregions the gray silver image was nonconductive. The electricallyconductive surface image had a resistivity of 0.1 ohm per square.

EXAMPLE XIII The first developer solution, Solution A, of a dualbathdeveloper was prepared using the method described in Example I forpreparing Solution A.

The second developer solution, solution M, of a dualbath developer wasprepared as follows:

Water to make up to 1000 ml.

A photographic film of the lithographic type as described in Example Iwas exposed as described in Example I. The exposed film was immersed inSolution A for two minutes and then washed with water for two minutes.The exposed film was immersed in Solution M for two minutes and thenwashed with water for two minutes. The film was dried at roomtemperature. A developed image was obtained with the normallyundeveloped areas having a continuous, silver metal, positive coatingwhich latter coating is electrically conductive. The surface areas ofthe film were measured for electrical conductivity. The unexposedregions of the film were electrically conductive while in the exposedregions the gray silver image was nonconductive. The electricallyconductive surface image had a resistivity of 0.15 ohm per square.

1 0 EXAMPLE XIV The first developer solution, Solution A, of a dualbathdeveloper was prepared using the method described in Example I forpreparing Solution A.

The second developer solution, Solution N, of a dualbath developer wasprepared as follows:

A photographic film of the lithographic type as described in Example Iwas exposed as described in Example I. The exposed film was immersed inSolution A for two minutes and then washed with water for two minutes.The exposed film was immersed in Solution N for two mintues and thenwashed with water for two minutes. The film was dried at roomtemperature. A developed image was obtained with the normallyundeveloped areas having a continuous, silver metal, positive coatingwhich latter coating is electrically conductive. The surface areas ofthe film were measured for electrical conductivity. The unexposedregions of the film were electrically conductive while in the exposedregions the gray silver image was nonconductive. The electricallyconductive surface image had a resistivity of 2.6 ohms per square.

EXAMPLE XV The first developer solution, Solution A, of a dual-bathdeveloper was prepared using the method described in Example I forpreparing Solution A.

The second developer solution, Solution 0, of a dualbath developer wasprepared as follows:

Water ml 700 Sodium sulfite (anhydrous) gm 60 p-aminophenol gm 5 Glucosegm 20 Tri-sodium phosphate gm 1 Salicylic acid gm 0.5Monomethylparaminophenol sulfate (reagent grade) gm 4 Potassiumthiocyanate (anhydrous) gm 30 Sodium sulfide (1 gram dissolved insufficient water to make up ml. of solution) ml 8 Sodium hydroxide (10grams dissolved in suflicient water to make up 100 ml. of solution) ml60 Water to make up to 1000 ml. pH=12.8.

A photographic film of the lithographic type as described in Example Iwas exposed as described in Example I. The exposed film was immersed inSolution A for two minutes and then washed with water for two minutes.The exposed film was immersed in Solution 0 for two minutes and thenwashed with water for two minutes. The film was dried at roomtemperature. A developed image was obtained with the normallyundeveloped areas having a continuous, silver metal, positive coatingwhich coating is electrically conductive. The surface areas of the filmwere measured for electrical conductivity. The unexposed regions of thefilm were electrically conductive while in the exposed regions the graysilver image was nonconductive. The electrically conductive surfaceimage had a resistivity of 0.25 ohm per square.

EXAMPLE XVI The first developer solution, Solution A, of a dual-bathdeveloper was prepared using the method described in Example I forpreparing Solution A.

The second developer solution, Solution P, of a dualbath developer wasprepared as follows:

Water ml 700 1-phenyl-4-methyl-3-pyrazolidone (reagent grade) gm 1Ascorbic acid gm Potassium carbonate "gm Potassium thiocyanate(anhydrous) gm 50 Sodium sulfide (1 gram dissolved in sufiicient waterto make up 100 ml. of solution) ml 8 Sodium hydroxide (10 gramsdissolved in suificient water to make up 100 ml. of solution) ml 15Water to make up to 1000 ml. pH: 10.4.

A photographic film of the lithographic type as described in Example Iwas exposed as described in Example I. The exposed film was immersed inSolution A for two minutes and then washed with water for two minutes.The exposed film was immersed in Solution P for two minutes and thenwashed with water for two minutes. The film was dried at roomtemperature. A developed image was obtained with the normallyundeveloped areas having a continuous, silver metal, positive coatingwhich latter coating is electrically conductive. The surface areas ofthe film were measured for electrical conductivity. The unexposedregions of the film were electrically conductive while in the exposedregions the gray silver image was nonconductive. The electricallyconductive surface image had a resistivity of 0.4 ohm per square.

EXAMPLE XVII The first developer solution, Soluton A, of a dual-bathdeveloper was prepared using the method described in Example I forpreparing Solution A.

The second developed solution, Solution Q, of a dualbath developer wasprepared as follows:

5-nitrobenzimidazole nitrate (reagent grade) (1 gram dissolved insufiicient ethanol and water, in equal portions, to make up 100 ml. ofsolution) ml Potassium thiocyanate (reagent grade) "gm 18 Thiourea (0.1molar solution) ml 4 Water to make up to 1000 ml.

A photographic film of the lithographic type as described in Example Iwas exposed as described in Example I. The exposed film was immersed inSolution A for two minutes and then washed with water for two minutes.The exposed film was immersed in Solution Q for two minutes and thenwashed with water for two minutes. The film was dried at roomtemperature. A developed image was obtained with the normallyundeveloped areas having a continuous, silver metal, positive coatingwhich latter coating is electrically conductive. The surface areas ofthe film were measured for electrical conductivity. The unexposedregions of the film were electrically conductive while in the exposedregions the gray silver image was nonconductive. The electricallyconductive surface image had a resistivity of 4.5 ohms per square.

EXAMPLE XVIII The first developer solution, Solution A, of a dual-bathdeveloper was prepared using the method described in Example I forpreparing Solution A.

The second developer solution, Solution R, of a dualbath developer wasprepared as follows:

Water ml 600 Sodium sulfite (anhydrous) "gm 40 sMonomethylparaminophenolsulfate (reagent grade) "gm 12 Hydroquinone (anhydrous) gm 20 Potassiumcarbonate (anhydrous) gm 20 Sodium hydroxide (10 grams dissolved insuflicient water to make up 100 ml. of solution) ml 1205-nitrobenzimidazole nitrate (1 gram dissolved in sufiicient ethanol andwater, in equal portions, to make up 100 ml. of solution) ml 10 Sodiumselenide (0.1 molar solution) ml 8 Potassium thiocyanate (reagent grade)gm 10 Water to make up to 1000 ml.

A photographic film of the lithographic type as described in Example Iwas exposed as described in Example I. The exposed film was immersed inSolution A for two minutes and then washed with water for two minutes.The exposed film was immersed in Solution R for two minutes and thenwashed with water for two minutes. The film was dried at roomtemperature. A developed image was obtained with the normally undeveloed areas having a continuous, silver metal, positive coating whichlatter coating is electrically conductive. The surface areas of the filmwere measured for electrical conductivity. The unexposed regions of thefilm were electrically conductive while in the exposed regions the graysilver image was nonconductive. The electrically conductive surfaceimage had a resistivity of 4.5 ohms per square.

EXAMPLE XIX The first developer solution, Solution A, of a dualbathdeveloper was prepared using the method described in Example I forpreparing Solution A.

The second developer solution, Solution S, of a dualbath developer wasprepared as follows:

Water ml 600 Sodium sulfite (anhydrous) "gm Monomethylparaminophenolsulfate (reagent grade) 2,4-diaminophenol (reagent grade) "gm 9.4

Boric acid (H BO (crystals) "gm 5.5

Sodium hydroxide (24 grams dissolved in sufiicient water to make up ml.of solution) ml 40 S-nitrobenzimidazole nitrate (reagent grade) (1 gramdissolved in sufiicient ethanol and water, in equal portions, to make up100 ml. of solution) ml 80 Sodium sulfide (0.1 molar solution) ml 10Potassium thiocyanate gm 30 Water to make up to 1000 ml.

A photographic film of the X-ray type was exposed as described inExample I. The film comprised a highspeed bromoiodide emulsion, in whichthe silver salt contained approximately 1.5 mole percent silver iodideand 98.5 mole percent silver bromide, and which contained 200 grams ofgelatin per mole of silver halide, coated on both sides of a polyesterbase, and an antiabrasion layer over coated on each emulsion layer. Theexposed film was immersed in Solution A for two minutes and then washedwith water for two minutes. The exposed film was immersed in Solution Sfor two minutes and then washed with water for two minutes. The film wasdried at room temperature. A developed image was obtained with thenormally underdeveloped areas having a continuous, silver metal,positive coating which latter coating is electrically conductive. Thesurface of the film was measured for electrical conductivity. Theunexposed regions of the film were electrically conductive while in theexposed regions the gray silver image was nonconductive. Theelectrically conductive surface image had a resistivity of 4.5 ohms persquare.

13 EXAMPLE xx The first developer solution, Solution A, of a dual-bathdeveloper was prepared using the method described in Example I forpreparing Solution A.

The second developer solution, Solution T, of a dualbath developer wasprepared as follows:

S-nitrobenzimidazole nitrate (1 gram dissolved in suflicient ethanol andwater, in equal portions, to

make up 100 ml. of solution) ml 40 Sodium sulfide (0.1 molar solution)ml Potassium thiocyanate (anhydrous) gm 30 Water to make up to 1000 ml.

A photographic film of the lithographic type as described in Example Iwas exposed as described in Example I. The exposed film was immersed inSolution A for two minutes and then washed with water for two minutes.The exposed film was immersed in Solution T for two minutes and thenwashed with water for two minutes. The film was dried at roomtemperature. A developed image was obtained with the normallyundeveloped areas having a continuous, silver metal, positive coatingwhich latter coating is electrically conductive. The surface areas ofthe film were measured for electrical conductivity. The unexposedregions of the film were electrically conductive while in the exposedregions the gray silver image was nonconductive. The electricallyconductive surface image had a resistivity of 4.5 ohms per square. a

EXAMPLE XXI The first developer solution, Solution A, of a dual-bathdeveloper was prepared using the method described in Example I forpreparing Solution A.

The second developer solution, Solution B, of a dualbath developer wasprepared using the method described in Example I for preparing SolutionB.

A photographic film of the lithographic type was exposed as described inExample I. The film comprised a high contrast silver chloride-silverbromide ortho chro-' matically sensitized emulsion, in which the silversalt contained 20 mole percent silver bromide and 80 mole percent silverchloride, and which contained 110 grams of gelatin per mole of silverhalide, overcoated with a clear hardened gelatin layer, containingsilica particles, and a polyester base coated with a dyed gelatin-NHbacking. The exposed film was immersed in Solution A for two minutes andthen washed with water for two minutes. The exposed film was immersed inSolution B for two minutes and then washed with water for two minutes.The film was dried at room temperature. A developed image was obtainedwith the normally undeveloped areas having a continuous, silver metal,positive coating which latter coating is electrically conductive. Thesurface areas of the film were measured for electrical conductivity. Theunexposed regions of the film were electrically conductive while in theexposed regions the gray silver image was nonconductive. Theelectrically conductive surface image had a resistivity of 1.0 ohm persquare.

EXAMPLE XXII The first developer solution, Solution A, of a dualbathdeveloper was prepared using the method described in Example I forpreparing Solution A.

The second developer solution, Solution B, of a dualbath developer wasprepared using the method described in Example I for preparing SolutionB.

A photographic film of the lithographic type as described in Example Iwas exposed in a camera through the base of the film so that there waslateral image reversal. The exposed film was immersed in Solution A fortwo minutes and then washed with water for two minutes. The exposed filmwas immersed in Solution B for two minutes and then washed with waterfor two minutes. The film was dried at room temperature. A developedimage was obtained with the normally undeveloped areas having acontinuous, silver metal, positive coating which latter coating iselectrically conductive. The surface areas of the film were measured forelectrical conductivity. The unexposed regions of the film wereelectrically conductive while in the exposed regions the gray silverimage was nonconductive. The electrically conductive surface image had aresistivity of 0.1 ohm per square.

EXAMPLE XXIII The first developer solution, Solution A, of a dual-bathdeveloper was prepared using the method described in Example I forpreparing Solution A.

The second developer solution, Solution B, of a dualbath developer wasprepared using the method described in Example I for preparing SolutionB.

A photographic film of the lithographic type as described in Example Iwas exposed by the contact exposure method. The contact exposure wasmade to a negative having a density greater than four. The exposed filmwas immersed in Solution A for two minutes and then washed with waterfor two minutes. The exposed film was immersed in Solution B for twominutes and then washed with water for two minutes. The film was driedat room temperature. A developed image was obtained with the normallyundeveloped areas having a continuous, silver metal, positive coatingwhich latter coating is electrically conductive. The surface areas ofthe film were measured for electrical conductivity. The unexposedregions of the film were electrically conductive while in the exposedregions the gray, silver image was nonconductive. The electricallyconductive surface image had a resistivity of 0.1 ohm per square.

EXAMPLE XXIV The first developer solution, Solution V, of a dual-bathdeveloper was prepared as follows:

Water ml 600 Sodium sulfite (anhydrous) gm Hydroquinone (anhydrous) gm16 Boric acid (H BO (crystals) gm 5.5

The second developer solution, Solution 13, of a dualbath developer wasprepared using the method described in Example I for preparing SolutionB.

A photographic film of the lithographic type as described in Example Iwas exposed as described in Example I. The exposed film was immersed inSolution V for two minutes and then washed with water for two minutes.The exposed film was immersed in Solution B for two minutes and washedwith water for two minutes. The film was dried at room temperature. Adeveloped image was obtained with the normally undeveloped areas havinga. continuous, silver metal, positive coating which latter coating iselectrically conductive. The surface areas of the film were measured forelectrical conductivity. The unexposed regions of the film wereelectrically conductive while in the exposed regions the gray silverimage was nonconductive. The electrically conductive surface image hadresistivity of 0.5 ohm per square.

EXAMPLE XXV A mono-bath developer, Solution Y, was prepared using themethod described in Example I for preparing 15 Solution B, except that45 grams of potassium thiocyanate (instead of 30 grams) were used inpreparing Solution Y.

Two pieces of photographic film of the X-ray type as described inExample XIX were exposed as described in Example I. The first exposedpiece of film was immersed in Solution Y for two minutes and then washedwith water for two minutes. The second exposed piece of film wasimmersed in Solution Y for four minutes and then washed with water fortwo minutes. Both pieces were dried at room temperature. A developedimage was obtained in each piece with the normally undeveloped areashaving a continuous, silver metal, positive coating which iselectrically conductive. The surface areas of the pieces of film weremeasured for electrical conductivity. The unexposed regions wereelectrically conductive, while in the exposed regions the gray silverimage was nonconductive. The electrically conductive surface image ofthe first piece of film had a resistivity of ohms per square and thesecond piece had a resistivity of 4.5 ohms per square.

EXAMPLE XXVI A mono-bath developer, Solution Z, was prepared as Water tomake up to 1000 ml.

A photographic film of the lithographic type as described in Example Iwas exposed as described in Example I. The exposed film was immersed inSolutio Z for two minutes and then washed with water for two minutes.The film was dried at room temperature. A developed image was obtainedwith the normally undeveloped areas having a continuous, silver metal,positive coating which latter coating is electrically conductive. Thesurface areas of the film were measured for electrical conductivity. Theunexposed regions of the film were electrically conductive while in theexposed regions the gray silver image was nonconductive. Theelectrically conductive surface image had a resistivity of 2.0 ohms persquare.

EXAMPLE XXV II A mono-bath developer, Solution Z, was prepared using themethod described in Example XXVI for preparing Solution Z.

A photographic film of the lithographic type as described in Example Iwas exposed as described in Example I. The exposed film was washed inwater for five minutes, immersed in Solution Z for two minutes and thenwashed with water for two minutes. The film was dried at roomtemperature. A developed image was obtained with the normallyundeveloped areas having a continuous, silver metal, positive coatingwhich latter coating is electrically conductive. The surface areas ofthe film were measured for electrical conductivity. The unexposedregions of the film were electrically conductive while in the exposedregions the black silver image was nonconductive. The electricallyconductive Surface image had a resistivity of 0.4 ohm per square.

l a EXAMPLE xxvrn The first developer solution, Solution AA, of adualbath developer was prepared as follows:

Water ml 800 Sodium sulfite (anhydrous) gm Hydroquinone (anhydrous) gm16 1-phenyl-4-methyl-3-pyrazolidone gm 1 Boric acid (H BO (crystals) ml5.5 Sodium hydroxide (24 grams dissolved in sufficient water to make upml. of solution) ml 100 S-nitrobenzimidazole nitrate (1 gram dissolvedin sufficient ethanol and water, in equal portions, to make up 100 ml.of solution) ml 8 Water to make up to 1000 ml.

The second developer solution, Solution Z, of a dualbath developer wasprepared using the method described in Example XXVI for preparingSolution Z.

A photographic film of the lithographic type as described in Example Iwas exposed as described in Example I. The exposed film was immersed inSolution AA for two minutes, and then washed with water for fiveminutes. The exposed film was immersed in Solution Z for two minutes andthen washed with water for two minutes. The film was dried at roomtemperature. A developed image was obtained with the normallyundeveloped areas having a continuous, silver metal, positive coatingwith latter coating is electrically conductive. The surface areas of thefilm were measured for electrical conductivity. The unexposed regions ofthe film were electrically conductive while in the exposed regions thegray silver image was nonconductive. The electrically conductive surfaceimage had a resistivity of 5 ohms per square.

EXAMPLE XXIX The first developer solution, Solution BB, of a dualbathdeveloper was prepared as follows:

Water ml 600 Hydroquinone (anhydrous) gm 9 Sodium sulfite (anhydrous) gm50.2 Potassium carbonate gm 50.2 Potassium bromide gm 4.5Monomethylparaminophenol sulfate gm 3 Water to make up to 1000 ml.

The second developer solution, Solution Z, of a dualbath developer wasprepared using the method described in Example XXVI for preparingSolution Z.

A photographic film of the lithographic type as described in Example Iwas exposed as described in Example I. The exposed film was immersed inSolution BB for two minutes and then washed with water for five minutes.The exposed film was immersed in Solution Z for two minutes and thenwashed with water for two min utes. The film was dried at roomtemperature. A developed image was obtained with the normallyundeveloped areas having a continuous, silver metal, positive coatingwhich latter coating is electrically conductive. The surface areas ofthe film were measured for electrical conductivity. The unexposedregions of the film were electrically conductive, while in the exposedregions the gray silver image was nonconductive. The electricallyconductive surface image had a resistivity of 1 ohm per square.

EXAMPLE XXX The first developer solution, Solution CC, of a dual-bathdeveloper was prepared as follows:

Water to make up to 1000 ml.

17 The second developer solution, Solution DD, of a dualbath developerwas prepared as follows:

Water ml 500 Sodium sulfite (anhydrous) gm 130 Hydroquinone (anhydrous)gm 3.2 3-phenyl-2-pyrazolidone gm 0.2 Sodium hydroxide grams insufiicient water to make up 100 ml. of solution) ml 95 Boric acid (H BO(crystals) gm 4.4 Sodium sulfide (0.1 molar solution) ml 8S-nitrobenzimidazole nitrate (1 gram dissolved in sufficient water andethanol, in equal portions, to

make up 100 ml. of solution) ml 65 Water to make up to 1000 ml.

A photographic film of the lithographic type was exposed as described inExample I. The film comprised a high contrast, silver chloride-silverbromide, orthochromatically sensitized emulsion, in which the silversalt contained 30 mole percent silver bromide and 70 mole percent silverchloride, which contained 67 grams of gelatin and 22 grams ofpolyethylacrylate latex per mole of silver halide, and which isovercoated with a clear hardened gelatin layer, containing silicaparticles, and a base coated with a dyed gelatin-NH backing. The exposedfilm was immersed in Solution CC for one minute and then with water forten minutes. The exposed film was immersed in Solution DD for fourminutes and then washed with water for five minutes. The film was driedat room temperature. A developed image was obtained with the normallyundeveloped areas having a continuous, silver metal, positive coatingwhich latter coating is electrically conductive. The surface areas ofthe film were measured for electrical con ductivity. The unexposedregions of the film were electrically conductive while in the exposedregions the gray silver image was nonconductive. The electricallyconductive surface image had a resistivity of 4.5 ohms per square.

EXAMPLE XXXI The first developer solution, Solution A, of a dual-bathdeveloper was prepared using the method described in Example I forpreparing Solution A.

The second developer solution, Solution EE, of a dualbath developer wasprepared using the method described in Example I for preparing SolutionB, except that barium sulfide solution was used in place of sodiumsulfide solution in preparing Solution BE.

A photographic film of the lithographic type as described in Example Iwas exposed as described in Example I. The exposed film was immersed inSolution A for two minutes and then washed with water for two minutes.The exposed film Was immersed in Solution EE for two minutes and thenwashed with water for two minutes. The film was dried at roomtemperature. A developed image was obtained with the normallyundeveloped areas having a continuous, silver metal, positive coatingwhich latter coating is electrically conductive. The surface areas ofthe film were measured for electrical conductivity. The unexposedregions of the film were electrically conductive while in the exposedregions the gray silver image was nonconductive. The electricallyconductive surface image had a resistivity of 4.5 ohm per square.

EXAMPLE XXXII The first developer solution, Solution A, of a dual-bathdeveloper was prepared using the method described in Example I forpreparing Solution A.

The second developer solution, Solution FF was prepared as follows:

Water ml 400 Sodium sulfite (anhydrous) gm 120 Hydroquinone (anhydrous)gm 4 1-pheny1-3-pyrazolidone (reagent grade) gm 0.25 Boric acid (H BO(crystals) gm 5.5

Sodium hydroxide (10 grams dissolved in sufiicient Hydrogen sulfide wasbubbled through Solution FF for 15 minutes at the rate of 2 liters perminute. Water was added to Solution FF to make up one liter of solution.

A photographic film of the lithographic type as described in Example Iwas exposed as described in Example I. The exposed film was immersed inSolution A for two minutes and then washed with water for two minutes.The exposed film was immersed in Solution FF for two minutes and thenwashed with water for two minutes. The film was dried at roomtemperature. A developed image was obtained with the normallyundeveloped areas having a continuous, silver metal, positive coatingwhich latter coating is electrically conductive. The surface areas ofthe film were measured for electrical conductivity. The unexposedregions of the film were electrically conductive while in the exposedregions the gray silver image Was nonconductive. The silveryelectrically conductive surface image had a resistivity of 4.5 ohms persquare. This example helps demonstrate the broad principle that anycompound (or compounds) that decomposes to the sulfide ion, or is asoluble sulfide, will behave as the necessary nucleating agent in thisnovel process. It may be said that the same statement applies in thecase of selenides.

In this invention the silver halide emulsion layer is preferablyovercoated with the transparent receptive layer of gelatin which mayalso act as an antiabrasion layer. It is this layer that the nucleatingagents, complex silver ions, and developer interact within to form theelectrically conductive silver. This layer must be a hard, nonremovable,water permeable layer which is uncleated after exposure and duringdevelopment. Any silica, or similar materal, in this layer may improvethe process results, but it is not essential. When the nucleating agentis applied prior to exposure over an emulsion layer without anantiabrasion layer, or in, or on the antiabrasion layer, the resultantelectrically conductive image is often of poor quality.

The water-soluble nucleating agent must be capable of diffusing throughan oleophobic, water-permeable binder. Examples of this type ofnucleating agent are sodium and potassium sulfides, sodium and potassiumselenides, sodium and potassium thiocyanates, thiourea and bariumsulfide. Also, the water-soluble sulfide or selenide can be produced inthe developer itself in a variety of ways of which Example XXXV is anillustration. The concentration of the nucleating agent in the developersolution varies with the type of developer and with the type of filmused. The operable concentrations are readily determined in each case byrelatively simple laboratory techniques; optimum concentrations aredetermined in the same manner.

The silver halide solvent can be a thiosulfate or a thiocyanatecompound.

In general development time is important. If development time is tooshort, the electrical conductivity of the image will be too low; ifdevelopment time is too long, the image will lose electricalconductivity. This occurs because too short a development time does notallow enough metallic silver to form, and excessive development timeallows the metallic silver to react with sulfide ions to formnonconductive silver sulfide. The optimum time,

agent, silver halide solvent, and developing agent.

Any nonfogging developer can be used to develop the negative image, butascorbic acid or litho developers are the most desirable because oftheir low sulfite ion concentration.

A high-energy developer must be used in developing the unexposed regionsto obtain the electrically conductive silver surface images.

Monomethylparaminophenol sulfate, 2,4-diaminophenol/hydroquinone,p-aminophenol, p-aminophenol/monomethylparaminophenol sulfate,hydroquinone/monomethylparaminophenol sulfate, and hydroquinone aresingleand double-agent high-energy developers which give good results indeveloping the unexposed regions to obtain the electrically conductiveimages. If a monomethylparaminophenol sulfate or hydroquinone system isused, the pH should be greater than 11.75.

The following compounds are representative of 3-pyrazolidone silverhalide developing agents which are useful in the developer compositionsof this invention which are used to obtain electrically conductivesilver surface images.

1-phenyl-3-pyrazolidone l-p-tolyl-3-pyrazolidone 5-phenyl-3-pyrazolidone5-methyl-3-pyrazolidone 1-p-chlorophenyl-3-pyrazolidonel-phenyl-5-phenyl-3-pyrazolidone l-m-tolyl-3-pyrazolidone1-phenyl-S-methyl-3-pyrazolidone l-p-tolyl-5-phenyl-3-pyrazolidonel-m-tolyl-3-pyrazolidone 1-p-methoxyphenyl-3-pyrazolidonel-acetamidophenyl-3-pyrazolidone1-phenyl-2-acetyl-4,4-dimethyl-3-pyrazolidonel-phenyl-4,4-dimethyl-3-pyrazolidone1-m-aminophenyl-4-methyl-4-propyl-3-pyrazolidone1-o-chlorophenyl-4-methyl-4-ethyl-3-pyrazolidone (17)l-m-acetamidophenyl-4,4-diethyl-3-pyrazolidone 1 8 1-(p-B-hydroxyethylphenyl) -4-dimethyl-3- pyrazolidone (19)1-p-hydroxyphenyl-4,4-dimethyl-3-pyrazolidone (20)1-p-methoxyphenyl-4,4-diethyl-3-pyrazolid0ne (21)1-p-tolyl-4,4-dimethyl-3-pyrazolidone pyrazolidone (23).l-p-diphenyl-4,4-dimethyl-3-pyrazolidone (24)1-(p-fi-hydroxyethylphenyl)-3-pyrazolidone (25) l-o-tolyl-3-pyrazolidone(26) 1-o-tolyl-4,4-dimethyl-3-pyrazolidone (27)l-phenyl-4-methyl-3-pyrazolidone Examples of two and three componenthigh-energy developers, containing at least one 3-pyrazolidone agent,which are used in obtaining electrically conductive images, are1-phenyl-3-pyrazolidone/N-methyl 2 pyrazolidone/ hydroquinone,hydroquinone/ l-phenyl 3 pyrazolidone, ascorbicacid/l-phenyl-3-pyrazolidone, ascorbic acid/lphenyl 4methyl-3-pyrazolidone, and hydroquinone/ 1-phenyl-4-methyl-3-pyrazolidone.

Normally an electrically conductive silver surface image is obtainedwhen a two-agent developer is used for either the first, second, or bothbaths of a dual-bath developer, and the second bath contains anucleating agent and a silver halide solvent. The most preferredembodiment of a two-agent developer is shown in Example I.

In general, three variables, i.e., sulfide concentration, sulfiteconcentration, and silver halide solvent/developer concentration, mustbe optimized to obtain the best product.

An electrically conductive silver surface image can be formed without anadded sulfide, thiourea or similar compound. To accomplish this, monoordual-bath development is carried out using a high-energy developercontaining a thiocyanate compound which can act both as a nucleatingagent and silver halide solvent. Other silver halide solvents, eg.sodium thio u fi and/or nucleating agents may be used with thethiocyanate compound.

Another mode of this invention involves a mono-bath developer with asilver halide solvent, e.g., thiocyanate, but no sulfide or selenidecompound. Not all high-energy developers or films are operable usingthis mode, which comprises a pre-development water soak followed by amono-bath development to form the electrically conductive silver surfaceimage. This mode is represented by Example X. All developers, havingthiocyanate as a component, also have 8 present because of aerialoxidation of the thiocyanate.

Still another mode of this invention is represented by Examples XXVI andXXVII. A nucleating agent and silver halide solvent were present in themono-bath developer used in both of the above examples. In Example XXVIIa pre-development water soak was used, and the resistance of thepositive image was reduced by a factor of five over the positive imageof Example XXVI.

The same or different developing agents may be used in each bath of adual-bath developer. When a dual-bath developer is used, the nucleatingagent and the silver halide solvent are normally placed in the secondbath. The above restriction also applies when a single-agent developeris used in the first bath, and a two-agent developer in the second bath.A two-agent developer, which gives a conventional negative silver image,when used as the first bath for a two-bath developer, may also be usedfor sec- 0nd bath by adding a nucleating agent and silver halidesolvent. If a single-agent developer is used first, it also may 'be usedin the second bath with another appropriate developing agent, silverhalide solvent and nucleating agent. The foregoing discussion ofmono-bath and dualbath developers is in no way an all inclusive listingof possible developer combinations and was not meant to excludeoperative combinations which were not specifically mentioned.

The film preferably, should be sufficiently transparent so that it canbe exposed with radiant energy from the front or back. But a film doesnot have to be transparent, since it can be exposed from the front anddeveloped to give good electrically conductive, surface silver images. Apreferred method of film exposure is in a camera through the base sothat there is lateral image reversal.

The oleophobic organic colloid of the silver halide emulsion layer usedin this invention may be gelatin, or, in place of gelatin, other naturalor synthetic oleophobic colloidal binding agents. Such agents includewater-permeable or water-soluble polyvinyl alcohol and its derivatives,e.g., partially hydrolyzed polyvinyl acetates, polyvinyl ethers, andacetals containing a large number of extralinear CH CHOH groups;hydrolyzed interpolymers of vinyl acetate and unsaturated additionpolymerizable compounds such as maleic anhydride, acrylic andmethacrylic acid ethyl esters and styrene. Suitable colloids of the lastmentioned type are disclosed in U.S. Patents Nos. 2,276,322, 2,276,323and 2,347,811. The useful polyvinyl acetals include polyvinyl acetalaldehyde acetal, polyvinyl butyraldehyde acetal and polyvinyl sodium 0-sulfobenzaldehyde acetal. Other useful colloidal binding agents includepoly-n-vinyllactams of Bolton, U.S. Patent No. 2,495,918, the olephobiccopolymers of N- acrylamido alkyl betaines described in Shacklett, U.S.Patent No. 2,833,050, oleophobic cellulose ethers and esters, colloidalalbumin, zein and polyacrylamide.

Similarly, silver halide emulsion may be selected from well-knownemulsions containing silver chloride, silver bromide and silver iodide,or mixtures thereof, as well as containing optical and chemicalsensitizing agents, fogstabilizing compounds, emulsion hardeners,plasticizing compounds, wetting agents, toners and matting agents.

The film support for the emulsion layers used in the novel process maybe any suitable transparent plastic. For example, the cellulosicsupports, e.g., cellulose acetate, cellulose triacetate, cellulose mixedesters, etc. may

21 be used. Polymerized vinyl compounds, e.g., copolymerized vinylacetate and vinyl chloride, polystyrene and polymerized acrylates mayalso be mentioned. The film formed from the polyesterification productof a dicarboxylic acid and a dihydric alcohol made according to theteachings of Alles, U.S. Patent No. 2,779,684, and the patents referredto in the specification of that patent. Other suitable supports are thepolyethylene terephthalate/isophthalates of British Patent No. 766,290and Canadian Patent No. 562,672 and those obtainable by condensingterephthalic acid and dimethyl terephthalate with propylene glycol,diethylene glycol, tetramethylene glycol or cyclohexane 1,4-dirnethanol(hexahydro-p-xylene alcohol). The films of Bauer et al., U.S. Patent No.3,052,543, may also be used. The above polyester films are particularlysuitable because of their dimensional stability.

Paper is another example of a suitable support if the paper is coatedwith a water resisting and oleopho'bic layer, for example, with ahardened gelatin layer or superficially saponified cellulose acetate.Matting agents,-such as, titanium dioxide, silicon dioxide, bariumsulfate, in varying quantities, may be incorporated into such layers. Itis also possible to use plates consisting of metals, alloys or metaloxides coated metal as the support.

Besides immersing the film in the developer solution, other methods ofapplying the solutions can be used such as dip roll, hopper, spray andthe like so that a sufficient amount of solution is applied to thesurface. It is probable that a highly viscous developer could be placedon the emulsion to provide semi-dry processing.

After development, the film may be dried by any convenient method. If anoven, hot air, or some similar mode is used for drying, care should betaken not to allow the film to reach an excessive temperature that willdamage the film, cause the silver image to peel off, etc.

Inverse transfer development is also called silver transfer developmentand solution physical development.

This method of making electrically conductive silver surface images hasseveral advantages which include (i) high electrical conductivity in thesilver image regions, (ii) high electrical resistivity in the backgroundregions, (iii) few circuit breaks in the silver image, even in verynarrow circuit-type lines, (iv) rapid and easy processing, and (v)readily available developer components. An advantage of this system isthat an electrical circuit pattern for testing may be obtained with thespeed of a photographic system. This invention may be used to make acircuit board or may be used to allow the rapid check of the electricalcontinuity of a circuit board design. The resultant elements of thisprocess can be used whenever electrical conductive images are desired.Additional advantages of the invention reside in the fact that theelements containing electrically conductive surface images of highconductivity can be made in simple, rapid and effective manners that areconvenient and versatile.

I claim: 1. A process which comprises (a) forming a latent developablesilver halide image in a photographic element having a singledevelopable, water-permeable, macromolecular organic colloid-silverhalide emulsion layer, by irnagewise exposure of said layer to actinicradiation, washing the emulsion layer with water, and (b) forming bysilver transfer development an electrically conductive silver surfaceimage having a resistance not more than 5.0 ohms per square in theunexposed areas of an outer water-permeable organic colloid layer ofsaid photographic film element, and a difference in resistivity of atleast 1X10 times between the conductive coating and the exposed regionsby immersion in developing solution containing a silver halide reducingagent, a nucleating agent, and a silver halide solvent, and (c)passingan electrical current or impulse through 22 the said electricallyconductive silver surface image for utilization.

2. A process according to claim 1 wherein the outer water-permeableorganic colloid layer is the said silver halide emulsion layer.

3. A process according to claim 2 wherein the organic colloid of theouter water permeable organic colloid is gelatin.

4. A process according to the claim 3 wherein the silver halide of thesilver halide emulsion layer is silver chlorobromide.

5. A process according to claim 1 wherein the outer water-permeableorganic colloid layer is a thin waterpermeable organic colloid layerfree from radiation-sensitive silver salts that is contiguous with thesilver halide emulsion layer.

6. A process according to claim 1 wherein the outer water-permeableorganic colloid layer is a thin gelatin layer contiguous with the silverhalide emulsion layer which comprises gelatin.

7. A process according to claim 1 wherein said transfer development iscarried out in a single high-energy, silver halide aqueous developersolution containing a 1-aryl-3-pyrazolidone developing agent, sodium orpotassium thiosulfate or thiocyanate and sodium or potassium sulfide.

8. A process according to claim 1 wherein said surface image constitutesa printed electrical surface image.

9. A process which comprises (a) forming a latent developable silverhalide image in a photographic element having a single developable,water-permeable, macromolecular organic colloidsilver halide emulsionlayer, by imagewise exposure of said layer by actinic radiation, and

(b) forming by silver transfer development an electrically conductivesilver surface image having a resistance not more than 5.0 ohms persquare in the unexposed areas of an outer water-permeable organiccolloid layer of said photographic film element, and a difference inresistivity of at least 1 l0 times between the conductive coating andthe exposed regions by (l) immersion in a first developer solutioncontaining a silver halide reducing agent, (2) washing the emulsionlayer with Water, and (3) immersion in a second developer solutioncontaining a nucleating agent and a silver halide solvent,

(c) passing an electrical current or impulse through the saidelectrically conductive silver surface image for utilization.

References Cited UNITED STATES PATENTS 2,533,463 12/1950 Ives 96-642,612,450 9/1952 Land 96-76 XR 2,751,300 6/1956 James et 31.

2,843,485 7/1958 YutZy et a1 96-76 2,854,386 9/1958 Lyman et al 204-153,021,212 2/1962 King 96-64 XR 3,033,765 5/1962 King et a1.

3,155,507 11/1964 Blake 96-64 3,223,525 12/1965 Jonker et a1 96-36.2

OTHER REFERENCES Haist, G. M., et al., Organic Silver-Complexing Agentsfor Photographic Monobaths, Photographic Science and Engineering, vol.5, No. 4, July-August 1961, pp. 198203.

Sasai, A., et al., Studies on Photographic Monobaths ContainingPotassium Thiocyanate, Photo. Sci. and Eng, vol. 8, No. 5,September-October 1964, pp. 270-275.

NORMAN G. TORCHIN, Primary Examiner C. BOWERS, Assistant Examiner U.S.Cl. X.R.

